Light emitting illuminating devices are currently used in many different technical fields to photochemically cure light activated materials. For example, in the medical field, photodynamic therapy drugs, such as psoralens and hematoporhorins, are currently being prescribed to induce a chemical reaction upon the application of radiant energy in the 600-700 nanometer range. In the field of dentistry it is now conventional to use light emitting illuminating devices to cure dental restorative materials, in situ, within a patients mouth, as well as in the dental laboratory. Numerous commercial applications also exist where adhesives and coatings use light activated materials which are photochemically cured by application of a light emitting illuminating device.
In a conventional photocuring device a gas filled lamp such as a mercury vapor, metal halide, florescent, halogen lamp or laser is used as the light source to generate radiant energy. The traditional gas pressure discharge and halogen lamp causes the photocuring device to generate a substantial amount of heat during operation and therefor requires an adequate heat dissipating system. Accordingly, such devices are large and complex. Moreover, in the case of gas pressure discharge lamps and lasers, long fiberoptic bundles are needed to transmit light from the source to the point of application. These bundles are costly and prone to break.
Although optoelectronic semiconductor and solid state light emitting devices including solid state lasers are commercially available, the radiant energy output from a single one of such devices is much too low to be useful as a light source for use in a photocuring device particularly when compared to the radiant output energy of, for example, a conventional halogen lamp. However, if the output radiant energy from a multiple number of conventional solid state light emitting devices were to be combined in an efficient manner, the total optical power generated would be theoretically sufficient to cure light activated materials in many industrial, medical and dental applications. A portable photocuring device which is directed to the concept of combining a multiple array of solid state LED""s to produce a combined source of light for use in a photocuring device is taught in U.S. Pat. No. 5,420,776 and U.S. Pat. No. 5,634,711 respectively. The light output from the array of LED""s is transmitted through an optical light guide and condensed to form a single output beam of light in a fiber optic conduit. The arrangement taught in these patents does not adequately combine the output radiant energy from the LED""s without substantial loss of energy. This loss necessitates a larger number of solid state LED""s to produce an adequate output of light energy. The number of solid state LED""s which may be used is limited for a hand held device and increases the difficulty in handling the heat generated in a concentrated small area by a large number of closely packed LED""s. In some applications there may not even be sufficient space to package the required number of LED""S to provide adequate curing.
The present invention is directed to an optical waveguide concentrator for combining the output radiant energy from a plurality of optoelectronic light emitting devices with minimal loss of radiant energy to the surrounding atmosphere. The present invention is also directed to a light emitting photocuring device for use in combination with the optical waveguide concentrator for providing a controlled optical output from an array of individual solid state light emitting devices wherein the total light energy output is equal to the cumulative addition of the output radiant energy from each of the individual solid state light devices with minimal energy lost to the surrounding atmosphere. For purposes of the present invention an optoelectronic light emitting device may represent a single light source of any known type but preferably selected from the group consisting of solid state or semiconductor light emitting diode(s) i.e., xe2x80x9cLED""sxe2x80x9d, light emitting polymers and semiconductor lasers. In accordance with the present invention the LED""S may have different wave length outputs which can be selectively turned on or off. For example the illuminating device of the present invention may have diodes with a 360 nm wave length output as well diodes with a 470 nm wave length output. This configuration could be used to cure materials in the 300-400 nm range as well as materials in the 400-500 nm range.
The optical waveguide concentrator of the present invention comprises at least one solid optically transparent member having an input surface, an output surface, a sloping surface intersecting the input and output surface to form an acute angle thereto, and a plurality of optoelectronic light emitting devices mounted in a substantially circular array facing said input surface with each optoelectronic light emitting device having an optical axis directed to intersect the longitudinal axis of the concentrator. In the preferred embodiment the input surface can be either flat or convex, the sloping surface can be conical or hyperbolic and the output or exit surface can be flat or concave depending upon the selection of the sloping surface. The sloping surface should have a taper such that the acute angle, in cross section, lies between 5xc2x0 and 15xc2x0 with respect to a plane parallel to the longitudinal axis of the concentrator.
The photocuring device of the present invention comprises a housing having a longitudinal axis, a waveguide concentrator having at least one solid optically transparent member of frustoconical geometry aligned with its longitudinal axis concentric to the longitudinal axis of the housing and having, in cross section, a sloping surface with a tapered angle of between 5xc2x0 and 30xc2x0, an input and an output surface substantially intersecting the sloping surface, an array of optoelectronic light emitting devices mounted to face said input surface with the optical axis of each light emitting device directed to intersect the longitiudinal axis of the concentrator, a source of power for said array of optoelectronic light emitting devices, control means for controlling the output from said waveguide concentrator and a light guide having one section internal of said housing in alignment with said longitudinal axis and in physical proximity to said waveguide concentrator and a curved section extending from said housing external of said photocuring device. The waveguide concentrator may have a further inclined surface extending from the input surface to the conical surface in a plane lying at an angle to the plane of the input surface substantially equal to said tapered angle xc2x150% for mounting said array of optoelectronic light emitting devices with the optical axis of each optoelectronic light emitting device lying substantially perpendicular to said inclined surface.